* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Slide 1
X-inactivation wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Cancer epigenetics wikipedia , lookup
Genetic engineering wikipedia , lookup
Gene therapy of the human retina wikipedia , lookup
Epigenetics in stem-cell differentiation wikipedia , lookup
Minimal genome wikipedia , lookup
Gene expression profiling wikipedia , lookup
Genome (book) wikipedia , lookup
History of genetic engineering wikipedia , lookup
Microevolution wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Designer baby wikipedia , lookup
Point mutation wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Oncogenomics wikipedia , lookup
Primary transcript wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Chapter 11 How Genes Are Controlled PowerPoint® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Lectures by Chris C. Romero, updated by Edward J. Zalisko © 2010 Pearson Education, Inc. Figure 11.00 HOW AND WHY GENES ARE REGULATED • Every somatic cell in an organism contains identical genetic instructions. – They all share the same genome. – So what makes them different? • In cellular differentiation, cells become specialized in – Structure – Function • Certain genes are turned on and off in the process of gene regulation. © 2010 Pearson Education, Inc. Patterns of Gene Expression in Differentiated Cells • In gene expression – A gene is turned on and transcribed into RNA – Information flows from – Genes to proteins – Genotype to phenotype • Information flows from DNA to RNA to proteins. • The great differences among cells in an organism must result from the selective expression of genes. © 2010 Pearson Education, Inc. Gene Regulation in Bacteria • Natural selection has favored bacteria that express – Only certain genes – Only at specific times when the products are needed by the cell • So how do bacteria selectively turn their genes on and off? • This is the first organism scientist used to study gene regulation • Click here © 2010 Pearson Education, Inc. • An operon includes – A cluster of genes with related functions – The control sequences that turn the genes on or off • The bacterium E. coli used the lac operon to coordinate the expression of genes that produce enzymes used to break down lactose in the bacterium’s environment. © 2010 Pearson Education, Inc. • The lac operon uses – A promoter, a control sequence where the transcription enzyme initiates transcription – An operator, a DNA segment that acts as a switch that is turned on or off – A repressor, which binds to the operator and physically blocks the attachment of RNA polymerase © 2010 Pearson Education, Inc. Operon Regulatory Promoter Operator gene Genes for lactose enzymes DNA mRNA Protein RNA polymerase cannot attach to promoter Active repressor Operon turned off (lactose absent) Transcription DNA RNA polymerase bound to promoter mRNA Translation Protein Lactose Inactive repressor Lactose enzymes Operon turned on (lactose inactivates repressor) Figure 11.2 •Eukaryotic cells have more complex gene regulating mechanisms with many points where the process can be regulated, as illustrated by this analogy to a water supply system with many control valves along the way. Chromosome Unpacking of DNA DNA Gene Transcription of gene Intron Exon RNA transcript Processing of RNA Flow of mRNA through nuclear envelope Cap Tail mRNA in nucleus mRNA in cytoplasm Nucleus Cytoplasm Breakdown of mRNA Regulatory proteins Translation of mRNA In the figure to the left, look at all of the valves. These would be the points at which the process can be made to go faster, slower or to stop. Polypeptide Various changes to polypeptide Note that even the final protein is activated or broken down depending upon the second by second needs of the cell (or body) Active protein Breakdown of protein Figure 11.3-7 • X chromosome inactivation – Occurs in female mammals – Is when one of the two X chromosomes in each cell is inactivated at random • All of the descendants will have the same X chromosome turned off. © 2010 Pearson Education, Inc. • Repressor proteins called silencers – Bind to DNA – Inhibit the start of transcription • Activators are – More typically used by eukaryotes – Turn genes on by binding to DNA © 2010 Pearson Education, Inc. • RNA processing includes the – Addition of a cap and tail to the RNA – Removal of any introns – Splicing together of the remaining exons © 2010 Pearson Education, Inc. • In alternative RNA splicing, exons may be spliced together in different combinations, producing more than one type of polypeptide from a single gene. © 2010 Pearson Education, Inc. Exons 1 DNA RNA transcript 2 RNA splicing mRNA 1 2 3 5 4 3 2 1 4 3 5 or 5 1 2 4 5 Figure 11.6-3 • Eukaryotic mRNAs – Can last for hours to weeks to months depending upon their use in the cell – Are all eventually broken down and their parts recycled © 2010 Pearson Education, Inc. •The process of translation offers additional opportunities for regulation. Cutting Initial polypeptide Insulin (active hormone) Figure 11.7-2 SIGNALING CELL Secretion Signal molecule Plasma membrane Cell Signaling:this is the control of a cell from outside of the cell such as a hormone. The pathway is seen in the figure. Reception Receptor protein TARGET CELL Signal transduction pathway Transcription factor (activated) Nucleus Click here Response Transcription mRNA New protein Translation Figure 11.8-6 Homeotic genes • Master control genes called homeotic genes regulate groups of other genes that determine what body parts will develop in which locations. These are used on a fertilized egg in preparation for building a fetus. Undifferentiated cells must have new genes expressed while others are silenced. Click here © 2010 Pearson Education, Inc. DNA Microarrays: Visualizing Gene Expression • A DNA microarray allows visualization of gene expression. It shows which genes are “turned on” • The pattern of glowing spots enables the researcher to determine which genes were being transcribed in the starting cells. • Researchers can thus learn which genes are active in different tissues or in tissues from individuals in different states of health. © 2010 Pearson Education, Inc. CLONING PLANTS AND ANIMALS The Genetic Potential of Cells • Differentiated cells – All contain a complete genome – Have the potential to express all of an organism’s genes • Differentiated plant cells can develop into a whole new organism. © 2010 Pearson Education, Inc. Single cell Root of carrot plant Root cells in growth medium Cell division in culture Young plant Adult plant Figure 11.12-5 • The somatic cells of a single plant can be used to produce hundreds of thousands of clones. • Plant cloning – Demonstrates that cell differentiation in plants does not cause irreversible changes in the DNA – Is now used extensively in agriculture • Regeneration – Is the regrowth of lost body parts – Occurs, for example, in the regrowth of the legs of salamanders © 2010 Pearson Education, Inc. Reproductive Cloning of Animals • Nuclear transplantation – Involves replacing nuclei of egg cells with nuclei from differentiated cells – Has been used to clone a variety of animals – Click here © 2010 Pearson Education, Inc. Reproductive cloning Donor cell Nucleus from donor cell Implant embryo in surrogate mother Clone of donor is born Therapeutic cloning Remove nucleus from egg cell Add somatic cell from adult donor Grow in culture to produce an early embryo Remove embryonic stem cells from embryo and grow in culture Induce stem cells to form specialized cells for therapeutic use Figure 11.13-5 Figure 11.13a Practical Applications of Reproductive Cloning • Other mammals have since been produced using this technique including – Farm animals – Control animals for experiments – Rare animals in danger of extinction © 2010 Pearson Education, Inc. (c) Clones of endangered animals Mouflon calf with mother Gaur Banteng Gray wolf Figure 11.14c Human Cloning • Cloning of animals – Has heightened speculation about human cloning – Is very difficult and inefficient • Critics raise practical and ethical objections to human cloning. • Click here © 2010 Pearson Education, Inc. Therapeutic Cloning and Stem Cells • The purpose of therapeutic cloning is not to produce a viable organism but to produce embryonic stem cells for the possible purpose of repairing failing organs or body parts. Bone marrow transplants. • • • Embryonic stem cells (ES cells) – Are derived from blastocysts – Can give rise to specific types of differentiated cells Adult stem cells – Are cells in adult tissues – Generate replacements for nondividing differentiated cells Unlike embryonic ES cells, adult stem cells – Are partway along the road to differentiation – Usually give rise to only a few related types of specialized cells © 2010 Pearson Education, Inc. Adult stem cells in bone marrow Blood cells Nerve cells Cultured embryonic stem cells Heart muscle cells Different culture conditions Different types of differentiated cells Figure 11.15 Umbilical Cord Blood Banking • Umbilical cord blood – Can be collected at birth – Contains partially differentiated stem cells – Has had limited success in the treatment of a few diseases © 2010 Pearson Education, Inc. Figure 11.16 THE GENETIC BASIS OF CANCER • In recent years, scientists have learned more about the genetics of cancer. • As early as 1911, certain viruses were known to cause cancer. • Oncogenes are – Genes that cause cancer – Found in viruses! • Proto-oncogenes are – Normal genes with the potential to become oncogenes – Found in many animals – Often genes that code for growth factors, proteins that stimulate cell division © 2010 Pearson Education, Inc. • For a proto-oncogene to become an oncogene, a mutation must occur in the cell’s DNA. • Click here © 2010 Pearson Education, Inc. Proto-oncogene (for protein that stimulates cell division) DNA Mutation within the gene Multiple copies of the gene Gene moved to new DNA position, under new controls New promoter Oncogene Hyperactive growthstimulating protein Normal growthstimulating protein in excess Normal growthstimulating protein in excess Figure 11.17 Tumor-suppressor gene Normal growthinhibiting protein Cell division under control (a) Normal cell growth Mutated tumor-suppressor gene Defective, nonfunctioning protein Cell division not under control (b) Uncontrolled cell growth (cancer) Figure 11.18 • Tumor-suppressor genes – Inhibit cell division – Prevent uncontrolled cell growth – May be mutated and contribute to cancer – Click here © 2010 Pearson Education, Inc. The Progression of a Cancer • Over 150,000 Americans will be stricken by cancer of the colon or rectum this year. • Colon cancer – Spreads gradually – Is produced by more than one mutation © 2010 Pearson Education, Inc. Colon wall Cellular changes: Increased cell division Growth of benign tumor Growth of malignant tumor DNA changes: Oncogene activated Tumor-suppressor gene inactivated Second tumor-suppressor gene inactivated Figure 11.19-3 • The development of a malignant tumor is accompanied by a gradual accumulation of mutations that – Convert proto-oncogenes to oncogenes – Knock out tumor-suppressor genes © 2010 Pearson Education, Inc. Chromosomes Normal cell 1 mutation 2 mutations 3 mutations 4 mutations Malignant cell Figure 11.20-5 “Inherited” Cancer • Most mutations that lead to cancer arise in the organ where the cancer starts. • In familial or inherited cancer – A cancer-causing mutation occurs in a cell that gives rise to gametes – The mutation is passed on from generation to generation © 2010 Pearson Education, Inc. • Breast cancer – Is usually not associated with inherited mutations – In some families can be caused by inherited, BRCA1 cancer genes but then they must be activated by environmental stimuli. If a woman carries the BRCA1 mutation, she has an 80% risk of developing breast cancer. © 2010 Pearson Education, Inc. Figure 11.21 Cancer Risk and Prevention • Cancer – Is one of the leading causes of death in the United States – Can be caused by carcinogens, cancer-causing agents found in the environment, including – Tobacco products – Alcohol – Exposure to ultraviolet light from the sun © 2010 Pearson Education, Inc. Table 11.2